Offset scissor and viewport when using SetDrawRectangle on surface.

gpu/ipc/service/direct_composition_surface_win.cc

Index: gpu/ipc/service/direct_composition_surface_win.cc
diff --git a/gpu/ipc/service/direct_composition_surface_win.cc b/gpu/ipc/service/direct_composition_surface_win.cc
index aea60f57a008658f164076b0161d7fe4c542590e..9454f787361fe6ff1eca8a0f557a58a889e2b946 100644
--- a/gpu/ipc/service/direct_composition_surface_win.cc
+++ b/gpu/ipc/service/direct_composition_surface_win.cc
@@ -295,7 +295,6 @@ bool DirectCompositionSurfaceWin::SetDrawRectangle(const gfx::Rect& rectangle) {
   ScopedReleaseCurrent release_current(this);
 
   RECT rect = rectangle.ToRECT();
-  // TODO(jbauman): Use update_offset
   POINT update_offset;
 
   HRESULT hr = dcomp_surface_->BeginDraw(
@@ -303,6 +302,8 @@ bool DirectCompositionSurfaceWin::SetDrawRectangle(const gfx::Rect& rectangle) {
   CHECK(SUCCEEDED(hr));
   has_been_rendered_to_ = true;
 
+  draw_offset_ = gfx::Point(update_offset) - gfx::Rect(rect).origin();
+
   g_current_surface = dcomp_surface_.get();
 
   std::vector<EGLint> pbuffer_attribs{
@@ -323,6 +324,10 @@ bool DirectCompositionSurfaceWin::SetDrawRectangle(const gfx::Rect& rectangle) {
   return true;
 }
 
+gfx::Vector2d DirectCompositionSurfaceWin::GetDrawOffset() const {
+  return draw_offset_;
+}
+
 scoped_refptr<base::TaskRunner>
 DirectCompositionSurfaceWin::GetWindowTaskRunnerForTesting() {
   return child_window_.GetTaskRunnerForTesting();